The present invention relates generally to improvements in rollers for conveyors and, more particularly, to a conveyor roller of the type which is mounted on stub shafts.
Roller conveyors are commonly used in many industries to move packages or materials. In general, a conveyor roller comprises a plurality of individual rollers mounted between two parallel frames. The roller typically comprises a tube having a bearing in each end thereof which is rotatably journaled on a roller shaft that extends longitudinally through the tube. The roller shaft protrudes from each end of the roller tube and engages mounting holes in the frame.
Frequently, the roller shaft not only serves to mount the roller, but also functions as a structural element of the conveyor frame. In such cases, the ends of the shaft are drilled and tapped. Bolts extending from the outside of the frame are threaded into the tapped holes in the roller shaft to secure the frame members and rollers together. This approach to the construction of conveyors makes assembly of the conveyor time consuming and difficult. Moreover, this method of constructing conveyors makes it difficult to replace a single roller.
Another method to mount rollers in a conveyor frame is to use a roller having a through-shaft which is spring-loaded. In this case, the frame members are held together independently by a series of cross members rather than through the rollers. The rollers generally are installed after the frame is assembled. To install the roller, the shaft is moved axially against the force of the spring and xe2x80x9csnapsxe2x80x9d into place when the shaft aligns with the mounting hole in the frame member. This method makes assembly of the conveyor much simpler and facilitates the replacement of rollers when they become worn or defective.
Several attempts have been made in the past to eliminate through-shafts in the roller, In place of a single thru-shaft, separate stub shafts have been used to support opposing ends of the conveyor roller. Typically, these stub shafts are bolted to the conveyor frame before the frame is assembled. The conveyor roller is then inserted over the stub shaft as the frame is locked together to create a final assembly. This method of mounting rollers in conveyors also makes assembly difficult. Moreover, this method essentially precludes prefabrication of the conveyor frame.
Accordingly, there is a need for a new method for mounting conveyor rollers in a frame which does not rely on a through-shaft extending through the roller, allows prefabrication of the conveyor frame, and facilitates ease of assembly.
The present invention combines the advantages of spring-loaded shafts, which make installation of the roller quick and easy, and a shaftless design which eliminates the need for a longitudinal through-shaft. To achieve these advantages, the present invention utilizes a sliding stub shaft which is spring-biased to an extended position. The stub shaft can be pushed inward against the force of the spring to allow insertion of the roller into a prefabricated frame. When the stub shaft aligns with the mounting holes in the frame, the spring pushes the stub shaft outward to engage the mounting hole. One advantage of the present invention is that it enables quick and easy assembly of a conveyor. The conveyor frame can be prefabricated at the factory while the rollers are installed on site. Further, the present invention allows for easy replacement of a worn or defective roller without the need to disassemble an entire conveyor section.
The spring-biasing of the stub shaft also produces advantages not before realized in conveyors. The spring-biasing tends to center the roller after it is installed so that its rotating members do not rub against either frame member. The spring also allows shock absorption to take place when packages or other conveyed materials are moved laterally across the conveyor as they are loaded or unloaded. Furthermore, the constant preload on the springs eliminates vibration and noise which would resonate through the conveyor frame structure.
Yet another advantage of the present invention is its reduced weight. By eliminating a through-shaft that extends through the roller tube and replacing it with two smaller stub shafts, the total weight of the conveyor roller is reduced. Since conveyors use many individual rollers, the total weight reduction in a conveyor can be substantial. This weight reduction makes the conveyors more portable in the event that the conveyors need to be moved from one place to another. Also, shipping costs are reduced.
Yet another advantage which is beneficial in the food handling industry, is the ability to produce a relatively low cost, non-corrosive conveyor roller. In the food handling and chemical industries, conveyor rollers frequently employ stainless steel through-shafts. Sometimes, the additional cost of stainless steel makes the installation and use of conveyor systems impractical from a cost standpoint. By eliminating the through-shaft in its entirety, the stub shaft can be supplied with sophisticated corrosion resistant materials. Because the parts are so small, it does not negatively impact the overall cost of the system.
Another feature of the conveyor roller is increased safety. The retention of the roller in the frame is assured even in the event of bolt failure or vibration which could cause the bolt to fall out. In either instance, the spring-loading bias on the stub shaft acts as a reductive retention system to prevent the roller from falling out of the frame.
Other objects and advantages of the present invention will become apparent and obvious from a study of the following description and the accompanying drawings.